Cable End Heater

Hot Junction Cable End Heater

When making the Measuring (hot) junction of MI Thermocouples and RTD’s it is advisable to keep the open end of the cable warm.
This avoids the slow ingress of moisture into the cable insulation, which would lower the Insulation Resistance. This parameter is important for high measurement integrity.

Keeping the cable warm also has a beneficial effect on the welding process.

1. Moisture in the insulation lowers both the resistance and the capacitance. If these two parameters become too low the high frequency component used to start the weld becomes corrupted. In extreme cases the spark will travel across the surface of the insulation and create weld spots and melting of the cable sheath. This is more prevalent with smaller cables which, although they have the same capacitance as their larger family members have increased voltage stress across the powder surface.

2. When making a sheath closure weld any moisture inside the cable begins to expand as the cable heats up. This affects the weld as the water vapour mixes in with the weld gas restricting the ionising process. In the extreme the expanding moisture creates a pressure differential within the weld causing the molten metal to rise up. (blown weld)

3. For both conductor welds and sheath closure welds the starting process is improved if the cable sheath or conductors are hot. This seems to affect the initial breakdown of the argon gas allowing a smoother more rapid start and less spluttering.

Most MI Thermocouple manufacturers properly store their cable prior to welding in large ovens. However when it comes to a warming facility close to the welding machine, there are no proprietary ovens on the market. Subsequently users have adopted a variety of ingenious and novel approaches, from hair dryers to domestic plate warmers.

TET Limited has developed a low cost Cable End Heater especially to fill this gap. The temperature is adjustable between 100°C and 150°C (212°F to 300°F).
The heater can be mounted directly on top of the bench either free standing or screwed down using the mounting plates provided.
The heater can also be screwed below the bench using reversed mounting plates.

The outside temperature of the heater is never greater than 40 C for a 20°C ambient.

A variation of the bench-top-mounted unit includes a PTFE powder-dispensing bottle fitted in the oven top to provide a source of warm dry powder for back-filled Thermocouples and RTD’s.

This model comes with two interchangeable bottles –one for 300-mesh powder and one for 60-mesh powder.

The TET Cable End Heater comes complete with an IEC power cable and spare fuse. A manual is provided for setting the set point temperature and changing from °C to °F

The heater runs of 220/240Vac 50/60Hz.

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